Data communication formats and types of data have become diversified due to increase of a communication rate. Under such circumstances, there is a demand for improving communication quality through performing more efficient communication by optimizing a type of data and a communication method of the data.
In particular, in a radio LAN (Local Area Network), a method is known in which data compression is performed on a radio LAN. In this case, it has no effect even if a secondary compression is further applied to the data to which primary compression has already being applied. Rather, a transfer time may be increased for the operation processing required for the secondary compression.
In conjunction with the above description, Japanese Laid Open Patent Publication (JP-P2001-111432A) discloses a data compression control apparatus. This data compression control apparatus controls compression processing of data to be transmitted, and includes a compression section adapted to compress the data, and a path selection section adapted to select a processing path for the data to be transmitted. The path selection section determines whether or not to compress the data to be transmitted by the compression section in accordance with a physical or logical type of a communication interface that transmits the data.
Also, Japanese Laid Open Patent Publication (JP-P2001-275112A) discloses a data compression apparatus. This data compression apparatus is used for a data transmission apparatus, and includes a transmission mode selection section adapted to select a first transmission mode or a second transmission mode in accordance with data indicative of a type of input data. A data compression section compresses the input data and sends it out to a data output terminal. A switching section sends out the input data to the data output terminal in the first transmission mode and sends out the input data to the data compression section in the second transmission mode.
Japanese Laid Open Patent Publication (JP-P2004-064171A) discloses an information processing apparatus. This information processing apparatus transmits a digital video data through radio communication, and includes a first video data compression section to compress the digital video data with a first compression rate, and a second video data compression section to compress the digital video data with a second compression rate. A detection section detects the radio communication state. A switching section outputs the video data by switching one of the first video data compression section and the second video data compression section in accordance with the radio communication state detected by the detection section.
Also, Japanese Laid Open Patent Publication (JP-P2005-159774A) discloses an image transmission apparatus. This image transmission apparatus transmits and receives an image data via a telecommunication line, and includes an image input section adapted to input an image data. An image encoding section encodes the image data into a compressed image when the image data is not a compressed image, and re-encodes the compressed image with a different compression rate. A compressed image capacity detecting section detects a capacity of the compressed image. A transmission rate detecting section detects a transmission rate when transmitting the compressed image data. A transmission time calculation section calculates a transmission time of the compressed data based on the compressed image capacity that is detected by the compressed image capacity detecting section, and the transmission rate that is detected by the transmission rate detecting section. An image compression conversion determining section determines whether or not to compresses the compressed image further with a higher expression rate, based on the calculated transmission time. A condition storing section stores parameters for determination of whether or not to perform re-compression by the image compression conversion determining section.
Also, Japanese Laid Open Patent Publication (JP-A-Heisei 5-145437) discloses a data transmission system. This data transmission system includes a compression processing section for compressing a data. A data transmission time estimating section estimates from a speed of a communication line and a data compression time, a data transmission execution time spent for data transmission (from transmission of the data by applying compression processing to reception and decompression of the data) when the compression processing of the data is applied. The data transmission time estimating section estimates a data transmission execution time (from transmission of the data until reception of the data) when the compression processing is not applied. The data transmission time estimating section determines, before transmitting the data, whether to transmit the compressed data to which data compression processing is applied or the data to which the processing is not applied, based on the estimated transmission execution time. A data transmission executing section transmits the data based on the determination by the data transmission time estimating section.
Japanese Laid Open Patent Publication (JP-A-Heisei 10-294769) discloses a relay apparatus. This relay apparatus is connected to a computer network and exchanges communication data via the network. The relay apparatus includes a compression determination table which stores compression/non-compression of the communication data for each control data of protocol headers of the communication data, and the compression mode when the data is compressed. A control data obtaining section obtains control data that is registered in the datable, from the protocol header of the communication data. In a compression mode selecting section, a data compression determining section determines whether or not compression is necessary and the compression mode when being determined to perform the compression, in accordance with a corresponding compression type that is searched from the compression determination table by using the control data obtained by the control data obtaining section as a key. A data compression section generates compressed communication data by compressing the communication data when being determined by the compression determining section that compression of the communication data is necessary. A transmission section transmits the communication data when being determined by the data compression determining section that compression is unnecessary, and transmits the compressed communication data as the transmission data when being determined that the compression of the communication data is necessary.